Formulating a Mixed Integer Programming Problem to Improve Solvability

A standard formulation of a real-world distribution problem could not be solved, even for a good solution, by a commercial mixed integer programming code. However, after reformulating it by reducing the number of 0-1 variables and tightening the linear programming relaxation, an optimal solution could be found efficiently. The purpose of this paper is to demonstrate, with a real application, the practical importance of the need for good formulations in solving mixed integer programming problems.